Primer pocket



5. A. SNELL PRIMER POCKET Nov. 6, 1945.

Filed Nov. 18, 1945 Emma F7. ENELL'H Patented Nov. 6, 1945 Samuel A.Snell, Jackson, Mich., assignor to Ryerson & Haynes, Inc., Jackson,Mich., a corporation of Michigan Application November 18, 1943, SerialNo. 510,755

2 Claims.

The present invention relates to the method of forming primer pocketsand flash holes for cartridge cases, the method having particularapplication to cartridge cases Where the primer extends part way intothe head of the case and communicates with the inside of the casethrough a flash hole, as in fifty caliber and twenty millimeterammunition.

Heretofore two methods have been generally used in forming primerpockets for cartridge cases. One method involves drilling and reaming,which has not proven entirely satisfactory due to the low rate ofproduction and the high percentage of rejections. Another method employsa coining operation in which the metal displaced by the coining punch isforced outwardly and increases the outside diameter of the head of thecartridge case in proportion to the amount of the metal displaced by thecoining punch. This method puts an extremely heavy load on the coiningtool with the result that the tools have a relatively short life andcausing frequent stoppage to replace worn and broken tools which slowsdown production'materially.

According to the present invention a new method is provided wherein thatpart of the metal displaced by the first indenting or roughing punch ispermitted to flow into the surrounding part of the head, increasing theoutside diameter in the usual manner. The next step is to punch or drilla hole through the head of the casing removing a volume of metalapproximately equal to or slightly in excess of the volume of metaldisplaced by the final tool, and causing the metal displaced by thefinal tool to flow inwardly practically closing the hole. The next andfinal step is to punch or drill the collapsed hole to the properdimensions for the flash hole.

Thus one of the objects of the present invention is to provide a methodfor increasing tool life and production in connection with the formingof primer pockets and flash holes for cartridge cases.

A further object is to provide a method wherein steps are provided of acharacter which facilitate the flow of metal and formation of primerpockets and flash holes in cartridge cases in a manner which will resultin increased tool life.

These and other objects and advantages residing in the present inventionwill more clearly appear from a consideration of the following matter.

In the drawing wherein one manner of carrying out the principles of thepresent invention is disclosed,

Fig. 1 is a cross-sectional view through a cartridge case showing thefirst coining step of the head,

Fig. 2 is a view similar to Fig. 1 showing a piercing or drillingoperation in the region of the flash hole,

Fig. 3 is a view similar to Fig. 1 showing the second coining operationproviding the finished primer pocket, and

Fig. 4 is a view similar to Fig. 1 showing the final steps of completingthe flash hole.

The preferred sequence of operation for carrying out the method of thepresent invention is illustrated in the drawing where, in Fig. 1, thecartridge case Ill, having a head I2, is shown with a, generallycone-shaped depression l4 formed by a coining or punching operationusing an indenting or roughing punch. The formation of the depression Min the head I2 will cause certain metal to flow in the head l2 outwardlyand upwardly, slightly increasing both the diameter and thickness of thehead I2. The next operation is to provide the hole I6 in the region ofthe flash hole, either by piercing or drilling operations. 'The thirdstep in my improved method is illustrated in Fig. 3, wherein a suitablepunch has brought the primer pocket [8 into finished form by enlargingthe generally conical depression I 4 shown in Fig. l. The enlargement ofthe depression I4 into the finished primer pocket I8 results in a flowof metal inwardly restricting or reducing the hole Hi to an irregularopening 20 shown in Fig. 3. The final operation in the formation of theprimer pocket and flash hole is illustrated in Fig. 4, and consists inpiercing or drilling the flash 1 hole 22 to its final form.

The operations above described may be advantageously carried out andperformed successfully in a punch press equipped with a dial feed,producing a finished primer pocket and flash hole at each stroke of thepress.

It has been foundin practice that by performing the above outlinedsequence of operations that the tool life has been materially increasedand breakage of tools reduced to a minimum. This has been accomplishedprimarily through the sequence of operations which facilitates the fiowof metal and provides some place for the metal to flow with greater easethan has been heretofore possible in accordance with standard practices.

What I desire to secure by Letters Patent and claim is:

1. The method of forming primer pockets for cartridge cases comprisingthe steps of forming a substantially cone-shape depression partlythrough the head of the cartridge case to permit displaced metal to flowoutwardly into the head of the case and leave a solid body of metalbetween the bottom of the depression and the inside of the cartridgecase, connecting the bottom of the cone-shaped depression to the insideof the cartridge case by a hole, shaping the coneshaped depression bypressure to a substantially 2. A method of forming primer pockets forcartridge cases comprising the steps of forming a depression in the headof the cartridge case by causing the metal to flow outwardly, providingan opening between said depression and the interior of the cartridgecase, shaping said depression intothe final form of the primer pocket bycausing'the metal to flow inwardly into said opening, and thereaftershaping said opening to cylindrical depression, permitting the displaced10 the final dimension of the flash hole.

metal to flow into the hole, and then enlarging the hole to form a flashhole between the primer pocket and th inside of the cartridge case.

SAMUEL A. SNELL.

